any difference in POI would only be subject to the different dynamic spine reaction(s) associated with a change in FOC since the pull of gravity is constant as related to arrow flight. "X" many grains will still be acted upon by the same force regardless of the distribution of the weight along the arrow's length.

any difference in POI would only be subject to the different dynamic spine reaction(s) associated with a change in FOC since the pull of gravity is constant as related to arrow flight. "X" many grains will still be acted upon by the same force regardless of the distribution of the weight along the arrow's length.

This is my problem on testing. Not sure how to get close enough.

The two arrows are 300 spine. One is a carnivor cut to 24.375. This one I put total of 300 gn up front. The second arrow is a fmj. Cut around 27.5 in. With a 150 gn tip.

All I can go by is total weight. Now I'm going to see if I can get a bullet hole in paper with both arrows. If so this should put most of the different flex between the two none void.

Yes they should be equal at the target. By the pull of gravity. But at this point there not. But I'm saying its drag. I'm removing that from the equation today.

But I'm going to consider if with in a inch of each other then it's flex,drag. If more then an inch then we can see if a high foc nose dives vs low foc.

How would one build a high FOC arrow that weighs the same as a lower FOC arrow? The lower would either have to be a stiffer, heavier shaft. The higher would have to be a front loaded lighter shaft. The difference in shaft lengths alone would create different dynamics leaving the bow.

How would one build a high FOC arrow that weighs the same as a lower FOC arrow? The lower would either have to be a stiffer, heavier shaft. The higher would have to be a front loaded lighter shaft. The difference in shaft lengths alone would create different dynamics leaving the bow.

At least that is how my "why even worry about it" brain sees it.

Yes and that is one part I cannot fix.

I thought I could use the ontarget spine program and try to match spine by program. But computer is down.

Both arrows I'm using should be stiff. So the flex should be at a minimum. This is why I'm allowing a 1 inch veriance.

I may be stepping out of line with this, but you also have to consider velocity of each.

The slower the velocity through a known distance allows gravity to act on the arrow longer, leading to greater fall at any distance. If two arrows are shot at equal height, trajectory, and velocity (gravity is constant 9.8 m/s/s) they should impact at the same point (+/-). This would apply as long as the coefficient of friction is equal for both arrows. Change velocity and faster arrow POI will be higher only because gravity is acting on the slower arrow for a longer period of time. Increase aerodynamic friction and a faster arrow may lose velocity fast enough to lower the POI.

I do not see FOC having that much affect.

OK, I am ready for everyone else to tell me I am wrong, and educate me, I love physics.

521.4 and 521.8 are not the same. They are very close, probably close enough to not make a measurable difference, but still not the same.

Won't stuffing an arrow with weight tubes affect the flex of the shaft, or at least alter it from what it would be if the weight were on the tip?

IMO there is no way to make a high GPI arrow that will have the same spine and flex characteristics as a high FOC arrow. The difference in shaft length required will make them perform completely different.